1. Field of the Invention
The present invention relates to a multiwavelength optical switch connected to a plurality of multiwavelength optical circuits, such as optical fibers which transmit a multiwavelength optical signal, and for carrying out circuit switching across channels of the same wavelengths.
2. Description of the Background Art
The following conventional circuit switching systems are described in Ken-ichi Yukimatsu et al., "Introduction to Optical Switching Technique", pp. 42-43, Ohm Limited, 1993, Tokyo, one of the references on conventional multiwavelength optical signals.
A first system demultiplexes a multiwavelength optical signal into a plurality of wavelengths with wavelength channel selectors provided for individual channels, and inputs the demultiplexed signals to an optical matrix switch for the individual channels, thereby outputting the signals from desired output ports. A second system splits a multiwavelength optical signal into signals which correspond in number to the number of output ports in terms of power, and then inputs them to a multiwavelength selecting filter, thereby outputting desired wavelength signals. A third system is configured by using 2.times.2 switches composed of acousto-optical (AO) transducers.
As another prior art, Masafumi KOGA et al. proposed an optical path cross-connect system based on a wavelength path concept in "Optical Path Cross-Connect System", Proceedings of the 1995 Communications Society Conference of the Institute of Electronics, Information and Communication Engineers of Japan.
In addition, Jacob Sharony et al. proposed a new class of dynamic wavelength-routing cross-connects in "The Wavelength Dilation Concept in Lightwave Networks--Implementation and System Considerations", Journal of Lightwave Technology, Vol. II, No. 5/6, May/June 1993, and Y. D. Jin et al. referred to dynamic wavelength router in "Performance Degradation Due to Crosstalk in Multiwavelength Optical Networks Using Dynamic Wavelength Routing", IEEE Photonics Technology Letters, Vol. 7, No. 10, October 1995.
The first system is thought to be most easily put into practice because it has low power loss and facilitates multiport configuration. A conventional multiwavelength highway switch to which M circuits are connected, each of M circuits being an N multiwavelength circuit, where M and N are natural numbers, includes wavelength demultiplexers and wavelength multiplexers, each connected for each one of the multiwavelength circuit at the input and output sides, and matrix switches provided for respective wavelengths.
Such a multiwavelength highway switch has a problem in that it cannot increase its integration size. This is because a multi-input wavelength demultiplexer and multiplexer that can accommodate a number of circuits belongs to an undeveloped technique, and hence it requires 2M wavelength demultiplexers and multiplexers at input and output sides, and a tri-dimensional configuration of 2N.times.M lines for interconnecting the demultiplexers and multiplexers with the matrix switches.